干气密封螺旋槽内润滑气膜的热力过程

基于滑移边界条件下的雷诺方程,不考虑密封环的变形,通过PH线性化方法、迭代法求解获得了气膜压力函数式.根据气膜微尺度流体流动过程中的熵变方程,得到了螺旋槽内气膜温度场分布.考虑微槽道内气流在不同阶段的熵变过程,分析了气膜温度场在不同多变指数下的分布规律,进而在不同多变指数下计算出密封环的热弹变形量及气膜厚度近似表达式,利用广义雷诺方程求解热弹变形下的气膜压力分布.在不同多变指数下对泄漏量进行计算并与无变形时的理论泄漏量进行比对.结果表明：随着气体从外径流入内径,槽内温度先升高后降低,密封环的变形量先增大后减小,泄漏量随变形量增大而变大,从而对密封性能产生影响.试验验证了泄漏量在采用不同多变指数时更接近于实际工况.这为螺旋槽干气密封的优化设计奠定了理论基础.

Thermodynamic process of lubricating gas film in dry gas seals with spiral grooves

An analytical pressure distribution function in the gas fibn is obtained by using the PH li- nearization and an iterative method without considering deformation of the seal rings based on the Rey- nolds equation under the sliding boundary conditions. From the equation relating to entropy change of micro-fluid flow in the spiral grooves, the temperature field in the gas film was obtained. The tempera- ture distribution in the gas film under the different polytropic exponents was analyzed by considering the process of entropy change of the fluid in the spiral groove. The thermo-elastic deformation of the seal rings and an approximate analytical formula for the gas fihn thickness were obtained for different poly- tropic exponent, the pressure distribution for the thermo-elastic deformation was worked out as well based on the generalized Reynolds equation. The leakage through the seals was predicted and com- pared with the theoretical one without deformation for different polytropic exponents. The resuhs de- monstrated that the highest temperature in the film appears inside the seals as a fluid flows inwards and the most significant deformation occurs there. The leakage was increased with deformation, eventuallyaffecting the sealing performance. The leakages under different polytropic exponents were much closer to the experimental measurements. The results can be used as a theoretical basis for optimization de- sign of dry gas seals.